Theory of crystal field in metals and magnetic anisotropy of rare-earth intermetallides

Experimental data and theoretical works on the magnetic anisotropy (MA) of rare-earth-transition metal intermetallic compounds are reviewed. Generalizations of the crystal field theory with an account of the conduction electron contribution are discussed. Discrepancies between the experimental data and the theoretical calculations of the MA constants, as well as between data obtained by different authors, are indicated. Using experimental Mossbauer and NMR spectroscopic data, possible values of effective charges are determined for R2T17-x compounds, which allow one to find the MA constants of these systems with different R and T in a unified way. The problem of the sign of the contribution from the rare-earth metal sublattice to the MA is discussed. The strong x dependence of this contribution in the R2Fe17-xTix system is treated in terms of the contribution to the crystal field from Ti ions in the dumbbells.